Test-retest reliability of hand-held dynamometric strength testing in young people with cerebral palsy

Arch Phys Med Rehabil. 2004 Jan;85(1):77-80. doi: 10.1016/s0003-9993(03)00379-4.


Objective: To evaluate the test-retest reliability of measuring lower-limb strength with a hand-held dynamometer in young people with cerebral palsy (CP).

Design: One rater measured the isometric strength of the lower limbs in 10 participants with CP on 2 occasions separated by 6 weeks.

Setting: University movement rehabilitation laboratory in Australia.

Participants: Ten young people (mean age +/- standard deviation, 13.5+/-3.4 y) with spastic diplegic CP. Eight of the participants walked independently and 2 walked with assistive devices.

Interventions: Not applicable.

Main outcome measures: Retest reliability of lower-limb strength, expressed in the units of measurement for the interpretation of group mean and individual scores and as intraclass correlation coefficients (ICC(2,1)).

Results: For groups, mean lower-limb strength increases of 7 kg (30%) could be interpreted as real change using 95% confidence intervals (CIs). For individuals, for strength gains to be interpreted as real change using 95% CIs, strength increases would need to be greater than 16.8 kg (70%) for the measurement of knee extension and to be greater than 4.3 kg (25%) for ankle plantarflexion. Measurement of hip extension strength was not reliable for group mean or individual scores. All reliability coefficients were greater than.80.

Conclusion: A hand-held dynamometer can reliably measure changes in lower-limb strength for groups of young people with CP. It is uncertain whether this method is useful for evaluating change in individuals. Relying only on a coefficient of reliability to decide the usefulness of a measurement can be misleading.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Cerebral Palsy / physiopathology*
  • Cerebral Palsy / rehabilitation*
  • Child
  • Female
  • Humans
  • Leg / physiopathology*
  • Male
  • Muscle, Skeletal / physiology
  • Reproducibility of Results